PHILADELPHIA (CBS) — A family get-together becomes a family die-together in You’re Next.

What starts out as the most generic of home-invasion horror flicks about a family reunion that turns deadly evolves into a thriller that’s scary, sure, but that’s legitimately enjoyable as well.

If it’s not quite a horror comedy, at least it manages a goodly number of dark laughs without undermining the scare quotient. And if it’s not quite a horror mystery, it does make you consider what Agatha Christie’s classics would be like if they featured gory explicitness with their multiple murders.

(3 stars out of 4)

The opening sequence is an act of invasion, violence, and death that sets the tension level for the rest of the film and ends with the film’s title scrawled in blood on the wall.

Then we move to the main body (make that bodies) of the film.

The well-fixed Cramptons (Rob Moran and Aubrey Davidson), celebrating their 35th wedding anniversary, have invited the other members of their dysfunctional family — their grown children (AJ Bowen, Amy Seimetz, Nicholas Tucci, and Joe Swanberg) and their significant others (Sharni Vinson, Ti West, Wendy Glenn, and Margaret Laney, respectively) -– to their vacation home deep in the woods.

Immediately, family members start doing what family members tend to do. But before you can say “sibling rivalry,” an arrow is shot through the window.

Then, invaders with crossbows and axes and knives (oh, my!) attack the house. And the cell phones are suddenly dead.

What awaits the terrified dinner hosts and guests outside is a gang of weapon-wielding thugs wearing animal masks. Exiting without being killed appears to be impossible.

It’s a game of survival, only it’s no game. What it is is a slaughterhouse. The hope it that someone at that dinner table is as adept at killing as the masked marauders.

And do the dysfunction dynamics diminish as the family fights for their very lives? Not even a little.

Horror specialist Adam Wingard (A Horrible Way to Die, Autoerotic, What Fun We Were Having), an expert scaremonger, is the film’s director and editor. His film is much more bloody and terrifying than it is playful and funny, but — despite a narrative that recalls 2008’s exercise in gorenography, The Strangers — You’re Next has more in common with this year’s Ethan Hawke thriller, The Purge, demonstrating that home invasion chillers needn’t be pointlessly sadistic and needn’t insult our intelligence, as The Strangers was and did.

That said, it’s still essentially a slasher flick, replete with horrifically graphic violence, even if it is miles away from torture porn. Still, any way you slice it, only horror buffs need apply.

Simon Barrett’s script, featuring an embedded surprise or two, is carefully crafted and is much more than just an excuse for bloodletting. It’s propelled by the question of just who these murderous interlopers are and why they’re doing what they’re doing.

And not only does it eventually follow through and fully answer all the questions raised, it also offers an interesting array of characters and uses gallows humor to relieve the tension, especially with regard to problematic relationships within the family — resentments and accusations and rivalries that not only never disappear but barely even step outside for a breath of air.

So we’ll scare up 3 stars out of 4 for a high-body-count family-under-siege thriller. You’re Next is brutal but bracing, draining but entertaining, bloody but bloody smart.